1108. Finding Average (20) sscanf() sprintf()

#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <string.h>
using namespace std;
//sscanf() – 從一個字元串中讀進與指定格式相符的資料
//sprintf() – 字元串格式化指令，主要功能是把格式化的資料寫入某個字元串中。
int main() {
    int n, cnt = 0;
    double sum = 0, t;
    char a[50], b[50];
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> a;
        sscanf(a, "%lf", &t);//從字元串中讀出
        sprintf(b, "%.2lf", t);//寫入字元串
        int flag = 0;
        for (int j = 0; j < strlen(a); j++) {
            if(a[j] != b[j]) flag = 1;
        }
        if(flag || t < -1000 || t > 1000) {
            printf("ERROR: %s is not a legal number\n", a); continue;
        }else{
            sum += t;
            cnt++;
        }
    }
    
    if(cnt == 0) cout << "The average of 0 numbers is Undefined\n";
    else if(cnt == 1) printf("The average of 1 number is %.2lf\n", sum);
    else printf("The average of %d numbers is %.2lf\n", cnt, sum / cnt);
    
    return 0;
}